(1) Field of the Invention
The present invention relates to an input device for performing handwritten input using a touch pad or a digitizer.
(2) Description of the Related Art
Conventionally known handwriting input devices include touch panels and digitizers which are attached to personal computers (PCs). These handwriting input devices allow freehand handwriting input using a finger tip or a stylus. For example, a user draws a picture using graphics software on a PC, by input using a stylus as if the user were writing characters or drawing images on an actual sheet of paper by handwritten input. Furthermore, for example, text is entered through handwritten character recognition by handwriting recognition software running on a PC, where hand-drawn character images are recognized as characters.
FIG. 1 shows appearance of a conventional input device. The conventional handwriting input device includes a PC 901, a digitizer 902, a stylus 903, and a display 904. The digitizer 902 and the display 904 are connected to the PC 901. The stylus 903 is a pen-shaped object for inputting handwritten characters into the digitizer 902. FIG. 1 shows that data of a trajectory of handwriting indicated by a dashed line is inputted into the digitizer 902 using the stylus 903, and is then displayed on the display 904.
It is to be noted that the inputting graphic data such as data of a completely straight line in the device shown in FIG. 1 is difficult because the data is based on handwritten data inputted freehand. FIG. 2 shows an exemplary conventional method of switching menu items on a conventional input device. The conventional exemplary method shown in FIG. 2 allows selection of menu items from a menu 905 displayed on the display 904 using the stylus 903. In other words, a user has to explicitly make a selection for switching input modes in the method. FIG. 3 shows a method of drawing a straight line in graphic mode. FIG. 3 shows an exemplary conventional method of drawing a straight line on a conventional input device. An operation of causing the stylus 903 to come into an instant contact with the digitizer 902 and immediately pulling away the stylus 903 from the digitizer 902, is hereinafter referred to as a tap or tapping. First, a user selects the graphic mode from the menu 905 by tapping. In graphic mode, the user inputs a start point and an end point of a straight line on graphics software running on the PC 901 by tapping twice, tapping once for each of the points, with the stylus 903 on an input surface of the digitizer 902. As a result, the graphics software draws a straight line which connects the start point and the end point. In order to draw a curve, the user selects the curve mode from the menu 905 by tapping on the menu item “Curve” with the stylus 903 to switch to the curve mode, in which a curve is drawn on the display 904 according to a trajectory of the stylus 903 as shown in FIG. 1.
However, there is a problem with the device shown in FIG. 1 that the device requires a user to explicitly switch modes, causing unavoidable laborious operations of the user and complex control of the device. Patent Reference 1 (Japanese Unexamined Patent Application Publication No. 2001-100902) discloses a device which allows a user to draw graphics without explicitly switching modes.
However, the device disclosed in Patent Reference 1 determines one of reference graphic patterns as a desired graphic pattern from a trajectory of input. The device replaces the trajectory with one of the reference graphic patterns when the trajectory falls within an effective scope calculated from the reference graphic patterns. In this case, a trajectory within an effective scope of a reference graphic patter is forcibly replaced with the reference graphic pattern even when the replacement is not necessary.